1. Field of the Invention
The present invention relates to grinding tools and, more particularly, to outdoor grinding tools, and also more particularly to rotating disc assemblies (including a disc, bit subassembly, and cutting bit shield/guard assembly).
2. Description of the Related Art
Stump cutting tools conventionally include a rotating disc assembly that includes a rotating disc and multiple bit sub-assemblies located at regular angular intervals on the peripheral edge of the rotating disc. For example, FIGS. 1 and 2 of U.S. Pat. No. 8,789,566 show a simplified conventional rotating disc assembly 100 including disc 102; and bit sub-assembly 104. Bit sub-assembly includes: bit holder 108; and bit 112. Conventional bit holder 108 provides a substantially rigid mechanical connection between the bit sub-assembly and the rotating disc so that there is substantially no relative motion between the bit sub-assembly and the rotating disc. Angular direction R shows the direction of rotation of the disc in operation.
Further, in FIG. 1 of U.S. Pat. No. 8,789,566, the bit sub-assembly 104 and its pocket 106 are centered at a twelve o'clock position over the center 107 of the disc. In FIG. 2 U.S. Pat. No. 8,789,566, at dotted area 112a, shows the view taken tangent to the top of the disc when the disc is in this twelve o'clock position of FIG. 1. It is this view that defines the “footprint” of the bit. This concept of a “footprint” will be important for understanding certain aspects of embodiments of present invention in the example of FIG. 1 and FIG. 2 of U.S. Pat. No. 8,789,366, the front face of the bit is substantially perpendicular to the viewing vector that defines the foot print of bit 112, but this is not necessarily always true in the prior art, or in embodiments of the present invention. Both the angular length (that is, angular length in direction R) of the bit sub-assembly and/of a non-orthogonal geometry for the bit itself can cause the front face of the bit to be non-perpendicular to the foot-print defining viewing vector. When the footprint of the bit is substantially perpendicular to the viewing vector, its footprint area will generally be at least approximately equal to the surface area of the front face of the bit. However, when the front face of the bit is not perpendicular to the viewing vector, then its footprint area will be less than the surface area of the front face of the bit.
In conventional usage, this idea of inclining the front face of the bit, forward or backward or not at all, relative to the footprint-defining viewing vector is called a “rake angle.” Conventionally, rake angle is adjusted by the grinder designer depending on factors such as soil type and/or rotational speed.
For present purposes, the important thing to note is that the footprint of the bit—that is, dotted area 112a taken perpendicular to the viewing vector—is entirely exposed as the disc rotates in direction R during operation of the grinder. More specifically: (i) no portion of disc 102 is interposed in front of the footprint when viewed from the viewing vector; and (ii) no portion of bit holder 108 or any other element positioned on the rotating disc is interposed in front of the footprint of the bit as its footprint is viewed from the viewing vector. Further, the bit only cuts in the “R” direction.
Description of the Related Art Section Disclaimer: To the extent that specific patents/publications/products are discussed above in this Description of the Related Art Section or elsewhere in this Application, these discussions should not be taken as an admission that the discussed patents/publications/products are prior art for patent law purposes. For example, some or all of the discussed patents/publications/products may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific patents/publications/products are discussed above in this Description of the Related Art Section and/or throughout the application, the descriptions/disclosures of which are all hereby incorporated by reference into this document in their respective entirety(ies).